Mobile devices, such as cellular telephones, communicate wirelessly with a communications network via, for example, base stations that serve a geographic area referred to as a cell. Some mobile devices are equipped with global positioning systems (GPS) and terrestrial positioning systems (TPS) that allow the mobile device to make location related measurements that can be used to determine location information for the mobile device. A mobile device with GPS or TPS can transmit some or all of the location related measurements and/or location information to a location server connected to the communications network. The location server may, for example, be an enhanced serving mobile location center (E-SMLC) or a secure user plane location (SUPL) location platform (SLP). The location server can provide assistance data to a mobile device to aid in determining the location of the mobile device. The location related measurements and/or location information received from the mobile device can be used by the location server for a variety of purposes, such as determining the location of the mobile device and determining assistance data that may be sent to other mobile devices.
One example of the above-mentioned exchange of location information and assistance data in a long term evolution (LTE) network is the LTE positioning protocol (LPP), which is a standard protocol defined by the 3rd Generation Partnership Project (3GPP). In LPP, a mobile device receives assistance data from the location server and a request for the mobile device to report location information back to the location server by a scheduled time. The mobile device makes measurements of Reference Signal Time Difference (RSTD), which is a measurement of the relative time difference between various base stations associated with nearby cells, and is the basis of an observed time difference of arrival (OTDOA) calculation. The mobile device then sends the results of the OTDOA calculation to the location server at the scheduled time.